The invention relates to a transfer device for hollow bodies printed or to be printed in a printing machine, such as sleeves, collapsible tubes, cans or the like, for transferring the hollow bodies between a supply conveyor means and a rotary, driven capstan plate, said capstan plate being associated with the printing means of the printing machine, and/or between the capstan plate and a removal conveying means.
For printing on hollow bodies having a round outer shape such as collapsible tubes, cans or the like printing machines are available, which have a rotary, driven capstan plate having receiving capstans arranged in sequence in the direction of rotation, on which the hollow bodies are held during the printing operation. During such operation the receiving capstans move along a curved path, moving past the printing means, on rotation of the capstan plate.
The hollow bodies to be printed are supplied to the capstan plate by a supply conveyor means, which as a rule has an endless, circulating conveyor chain, on which bearer rods are arranged mounting the hollow bodies to be supplied. In a similar manner the removal of already printed hollow bodies takes place using a removal conveyor means. In this case a minimum distance apart of the sequentially following hollow bodies in the conveyor means is strived at in order to achieve a minimum overall size and maximum conveying speed. If the distance apart of the hollow bodies were for example to be equal to the pitch of the receiving capstans on the capstan plate, this would also mean a larger overall volume of any associated dryers, through which the hollow bodies are caused to pass. In the same way, at a certain frequency (number of strokes per unit time) and with a larger chain pitch the speed of the conveyor chain must be increased, something which means an increased rate of chain wear and a larger drive power.
The resultant different pitch of the receiving capstans of the capstan plate present and of the carrier rods of the conveyor means leads to a transfer problem on transfer of the hollow bodies between the respective conveyor means and the capstan plate. To the knowledge of the assignee attempts have generally been made so far to tackle this problem by multi-stage transfer operations, the hollow bodies being transferred between the conveyor means and the capstan plate several times between transfer drums of increasing pitch and correspondingly different speeds of rotation. Owing to the large number of transfer points there is however a large space requirement. Furthermore, the transfer operations are still far from perfect because of the different drum speeds and still prevent high speeds of conveying of the hollow bodies being achieved.
The patent publication WO 97/07979 describes a further design of the transfer device, in the case of which a transfer drum arranged adjacent to the capstan plate is utilized; but here again the drum has the same dimensions as the capstan plate and this generally leads to extremely large dimensions.
One object of the invention is to create a transfer device which in a high speed environment renders possible a reliable transfer of hollow bodies between on the one hand the capstan plate and on the other hand a supply conveyor means, which serves for the supply of the hollow bodies, and/or a removal conveyor means serving for removal of the hollow bodies.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention a transfer device for hollow bodies printed or to be printed in a printing machine, such as sleeves, collapsible tubes, cans or the like, comprises:
a rotary driven transfer rotor for transferring hollow bodies, supplied sequentially by way of a supply conveyor means, to rotary driven a capstan plate associated with the printing device of the printing machine
and/or
a rotary driven transfer rotor for the transfer of already printed hollow bodies from the rotary driven capstan plate to a removal conveyor means,
holding units arranged at the transfer rotor sequentially in its direction of rotation, such holding units defining receiving sites for releasably holding hollow bodies to be transferred, which on rotation of the transfer rotor move along a first curved path, and receiving capstans serving for holding the hollow bodies during a printing operation, and which on rotation of the capstan plate move along a second curved path, the pitch of the holding units on moving past the supply and, respectively, removal conveyor means being matched to the spacing of the supplied and, respectively, removed hollow bodies and being smaller than the pitch of the receiving capstans on moving past the printing device,
the holding units and/or the receiving capstans being able to be steplessly set to vary their pitch in a direction perpendicular to the axis of rotation of the associated transfer rotor or, respectively, capstan plate,
means defining a transfer zone between the transfer rotor and the capstan plate, in which the hollow bodies are transferred between the receiving sites of the holding units of the transfer rotor and the receiving capstans of the capstan plate,
and control means, by means of which the adjustable holding units and/or the receiving capstans are so able to be positioned in relation to one another that receiving sites and receiving capstans, just participating in a transfer operation, move along identical curved paths in pairs with a coaxial alignment at the same speed.
This means that even at high conveying speeds and with an extremely low supply and, respectively, removal body to body distance in comparison with the pitch of the receiving capstans provided on the capstan plate, it is possible to ensure a neat, continuous hollow body transfer between on the one hand the capstan plate and on the other hand a supply conveyor means and/or a removal conveyor means. The printing machine fitted with the transfer device may also be run in the high speed range. Transfer between a respective conveyor means and the capstan plate is implemented by a rotary driven transfer rotor, which is fitted with holding units, which respectively define a receiving site for a hollow body. By varying the distance between the holding units and the axis of rotation of the transfer rotor and/or by variation of the distance between the receiving capstans and the axis of rotation of the capstan plate, it is possible to so influence the curved paths moved along by the receiving sites and the receiving capstans that in a transfer zone between the transfer rotor and the capstan plate they have an identical curved path of movement with an identical speed and pitch. On moving along this path it is possible for the hollow bodies to be reliably transferred between receiving sites, which are arranged in pairs coaxially to one another, and the receiving capstans.
In order to provide the desired identical curved path in the transfer zone with a identical pitch it is possible to have exclusively a corresponding positioning of the holding units of the transfer rotor. In principle an exclusive positioning of the receiving capstans for this purpose would also be possible. Furthermore a positioning both of the receiving sites and also of the receiving capstans is possible, in which respect it is convenient for the major part of the positioning adaptation to be using the holder units, whereas on the part of the receiving capstan only a small positioning, which could be termed a path correction, will take place.
At this point it is to be noted that in the present invention the term xe2x80x9cprintingxe2x80x9d or the like means any type of decoration of hollow bodies, any application of color or paint, labeling, foil embossing and screen printing coming into question. Accordingly the term xe2x80x9cprinting machinexe2x80x9d means any machine adapted for the decoration of the type in question as mentioned.
Further advantageous developments of the invention are defined in the claims.
The mutually parallel axes of rotation of the transfer rotor and of the capstan plate are preferably so offset in relation to each other that the axis of rotation of the transfer rotor is outside the or complete (full loop) curved path of the receiving capstans. The distance of the two axes of rotation from the transfer zone is conveniently identical. In operation, rotation of the transfer rotor and of the capstan plate take place in opposite directions so that in the transfer zone the receiving sites and the receiving capstans move along paths in the same direction.
The control means contributing to presetting the identical curved paths on passing through the transfer zone may in principle be exclusively electronic and cause the desired pitch adaptation in accordance with the respectively detected instantaneous angular position of the transfer rotor and/or of the capstan plate. However it is preferred to use mechanical control means in a complementary manner or exclusively, such control means comprising at least one closed (full loop) cam face, on which cam followers run, which cooperate with the holding units and/or with the receiving capstans, on rotation of the transfer rotor in order to produce the desired positioning movement.
The transfer rotor is preferably drum-like in structure, the holding units being located more particularly on the radially outwardly directed peripheral face of the transfer rotor.
The bearing means for the adjustable holding units and/or the receiving capstans on the associated main body of the transfer rotor or, respectively, of the capstan plate preferably involves the use of radially telescoping guide means.
In order to hold the hollow bodies during the transfer operation between a conveyor means and the capstan plate the holding units may have suitable vacuum holding means, which are responsible for a fixing action due to the negative pressure. However, other suitable holding means would be possible.
The direct transfer between the transfer rotor and the capstan plate is preferably effected by the holding units, which for this purpose may be mounted on bearing means for adjustment in a transfer direction parallel to the axis of rotation of the transfer rotor and in order to perform a hollow body transfer operation on moving through the transfer zone are caused to carry out a transfer movement in the transfer direction, same respectively transferring one hollow body between mutually coaxial pairs of receiving sites and receiving capstans. Dependent on the direction of transfer the hollow bodies are then either placed on the receiving capstans, or doffed by the holding units.
The transfer movement is preferably performed in a fashion dependent on the instantaneous angular position of the transfer rotor, for which purpose suitable control means are provided.
The transfer of the hollow bodies between a respective conveyor means and the transfer rotor may take place in a similar manner, there being the possibility of simplification in as far as no pitch matching is necessary. The supply conveyor means and/or the removal conveyor means may respectively include a conveyor chain with sequentially following carrier rods for the hollow bodies, which in a supply zone, or respectively removal zone, located between the respective conveyor means and the transfer rotor, run along a supply curved path or, respectively, removal path, such path being identical to the curved path of motion of the receiving sites of the holding units, the carrier rods and the receiving sites being associated in pairs generally coaxially, something which owing to the doffing and putting on of hollow bodies permits transfer of bodies during the passage along the supply or, respectively, removal path.
In order to ensure that a hollow body is transferred extremely exactly to the transfer rotor, the supply conveyor means may have a rotatable centering wheel in the supply zone having an axis of rotation parallel to the axis of rotation of the transfer rotor and with centering pockets which are distributed in the direction in the peripheral direction and are open in an outward direction. The conveyor chain is so arranged that in the region preceding the supply path it follows an entry curve as set by the pitch circle of the centering pockets, hollow bodies supplied in operation being placed sequentially in such centering pockets. The arrangement is furthermore such that in the transition zone between the entry curve and the supply curve centering pockets of the centering wheel and receiving sites of the transfer rotor meet in pairs so that the hollow bodies may be received by the holding units defining the receiving sites.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawings.